Rain gardens can help reduce soil pollution

Sunday

May 29, 2011 at 12:01 AMMay 29, 2011 at 9:29 PM

Home runoff comes down drain pipes, travels down driveways and across patios, sweeps over lawns and ends up in local streams. It carries with it pet waste, lawn chemicals, salt from the roads, oil and gas from cars and even traces of heavy metals.

Charlene Perkins Cutler

In the past decade, we have heard the term “non-point-source pollution” more frequently. I, for one, always connected that term with storm water runoff from large developments, eroded soils, or agricultural chemicals washed off of farm fields. In fact, one of the worst sources of these pollutants is the water running down house gutters during and after a storm. With more homes than any other kind of development in The Last Green Valley, this is a concern.

Home runoff comes down drain pipes, travels down driveways and across patios, sweeps over lawns and ends up in local streams. It carries with it pet waste, lawn chemicals, salt from the roads, oil and gas from cars and even traces of heavy metals.

As a concerned homeowner, I did some research on the subject and found a good solution was a garden — a rain garden. Think of a raised bed garden in reverse: A concave collecting point for water positioned downhill from a downspout, walk or driveway. That area is planted with a variety of plants that will thrive in such an environment. The flora serves as a filter to reduce toxins and pollutants, while the water is collected and allowed to seep naturally into the ground for further filtration. By the time it reaches the water table, it is clean. This is a very practical, efficient and, if I may say so, enjoyable solution. An effective rain garden does not have to be large because any rain water that seeps into the earth instead of running off will help prevent pollution.

Rain gardens are great projects for our communities as well as our homeowners. Areas like this in public parks, in neighborhood open spaces, and adjacent to community buildings would offer an opportunity to schools, Scout groups, garden clubs and others to participate in a real process to improve the ecology of their home and provide aesthetic value in our towns.

Aside from siting the rain garden downhill from a source of storm water, one needs to determine the absorption rate of the soil. If you dig a hole vertically into the area about eight or nine inches in diameter, the absorption can be tested by filling the hole with water once and refilling it in about a half hour. Then wait for four hours before measuring the water level from the top of the hole. The level at four hours multiplied by six will provide you with a rate of inches of water absorbed per 24 hours. That number will determine the depth of the rain garden. The depression is a gradually sloping structure, graded to the deepest point but with sides coming up gently to the natural elevation of the surrounding.

Once the depression has been dug to the correct depth, loosen up one or two inches of soil at the bottom and work in some compost. Plants that love wet environments go into the bottom of the garden. Those that like wet to average are placed up the sides, leaving the area around the top perimeter for the green things that prefer drier conditions. Once the plants are in place, add a couple of inches of mulch to tuck them in. One only needs to water them during a long, dry spell.

Plant selection is always the fun part. In this case, it is doubly gratifying that native plants can be used in the rain garden. And, of course, you should consider whether the rain garden is in a sunny or shaded location. Beebalm (Oswego tea, Monarda didyma) is a good choice and comes in several colors, although I prefer red. Joe-pye Weed (Queen of the Meadow, Eupatorium maculatum) is another with a rose-colored bloom that can be used as a dried flower. White turtlehead and cardinal flower are lovely choices, too. Winterberry is an excellent shrub for a rain garden, as is American elderberry.

I never need an excuse to consider creating a new garden, but this time I am energized by the knowledge that my little rain garden can help keep The Last Green Valley and its waterways healthy.

That sufficient reason to put other projects on hold and start this spring.

Charlene Perkins Cutler writes a column about The Last Green Valley that appears Sundays. Email her at Charlene@tlgv.org

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